A so-called fiber reinforced plastic (hereinafter, referred to as an “FRP”), which is a composite material in which a fiber material such as a glass fiber is used as a reinforcing material and a synthetic resin material is used as a matrix resin, provides a high mechanical strength per weight. Accordingly, the FRP is employed for various types of structural materials in vehicles and architectural buildings.
One of the methods for forming the FRP is a filament winding method. The filament winding method is a method for forming the FRP by winding around a mandrel, filament which is impregnated with a resin, and a filament winding apparatus is used for realizing the filament winding method.
The filament winding apparatus has a creel for accommodating therein, long fibers, roving which is formed in a thread state by making a bunch of long fibers, and filament which is a generic name referring to an elongated tape or the like which is formed by long fibers, in a take-up state, for example. Filament at tip end side which is drawn from the creel is wound around a core material that is referred to a “mandrel”.
A pre-heater and a resin impregnating reservoir are disposed between the creel and the mandrel. Filament which is drawn from the creel is passed through the pre-heater and the resin impregnating reservoir, while being forwarded to the mandrel.
Filament is subjected to dehumidification by passing through the pre-heater. Further, the dehumidified filament is passed through the resin impregnating reservoir, and is applied and impregnated with a thermosetting synthetic resin material. Thus, the filament which is impregnated with the synthetic resin material is passed through a ring-shaped thread-feeding opening and then entrained around the mandrel.
In this state, due to a rotation of the mandrel around a fixed shaft center, filament is sequentially wound, from tip ends thereof, around the mandrel with a predetermined pattern and a tensional force is caused by the filament being wound around the mandrel due to a rotation of the mandrel. Due to this tensional force, subsequent filament is drawn from the creel and wound around the mandrel. Further, the mandrel for which winding of filament has been completed is introduced into a hardening furnace, and the synthetic resin material is hardened.
By the way, ordinarily, the filament winding apparatus has a traverser mechanism. The traverser mechanism has guide rails which extend along the direction of an axial direction of a rotation of the mandrel. The thread-feeding opening is attached to the guide rails so as to be slidable in a lengthwise direction of the guide rails. Further, the guide rails have a ball screw or the like, and due to a driving force of driving means (mechanism) such as a motor, the ball screw allows the thread-feeding opening to slide in the lengthwise direction of the guide rails, in other word, an axial direction of a rotation of the mandrel.
In a state in which, due to a rotation of the mandrel, filament is wound around the mandrel, the thread-feeding opening is guided by the guide rails at predetermined timing and speed, and moved in a direction of the axial direction of a rotation of the mandrel. By this, a position at which filament is wound around the mandrel is changed in the axial direction of a rotation of the mandrel. For example, filament is wound around a predetermined region (including an entire region) of the mandrel in the axial direction of a rotation of the mandrel.
On the other hand, Japanese Patent Application Laid-Open (JP-A) No. 8-72156 discloses a filament winding apparatus having a structure in which, due to a driving force of a DC servo motor, a mandrel (it is referred to as a take-up type mandrel in JP-A No. 8-72156) is rotated, and moved back and forth in an axial direction of a rotation of the mandrel. In this way, the filament winding apparatus disclosed in JP-A No. 8-72156 is structured such that, during a rotation of the mandrel, the mandrel is moved back and forth in the axial direction of a rotation of the mandrel, and a position at which filament is taken up is changed in the axial direction of a rotation of the mandrel. Accordingly, filament (which is referred to as fiber in JP-A No. 8-72156) can be taken up around the mandrel without swinging the filament in a left-hand direction and a right-hand direction (i.e., the axial direction of a rotation of the mandrel).
On the other hand, examples of means for improving production efficiency in such a filament winding apparatus as described above include an increase of a rotational speed of the mandrel, in other words, an increase of a winding speed of filament. Due to an increase of the winding speed of filament, time from the beginning of winding to the end thereof can be reduced thus making it possible to enhance production efficiency.
However, in an ordinary filament winding apparatus in which a thread-feeding opening is moved in an axial direction of a rotation of a mandrel, a speed at which a thread-feeding opening is moved back and forth must be increased by increasing a speed at which filament is wound around the mandrel. For this reason, acceleration/deceleration of the thread-feeding opening is increased, whereby filament is swung largely between a creel which is a feeding portion of the filament, and the thread-feeding opening.
In this way, by filament being swung largely, distortion or twisting of the filament may occur resulting into scuffing thereon, or deterioration of a forming quality due to unexpected change of tension at the filament may occur.
Further, as another means for improving production efficiency, it can be considered to provide a plurality of arrangements from a creel to a thread-feeding opening (hereinafter, which is referred to as a “filament feeding arrangement”), and wind a plurality of filaments around a mandrel at one time. In this way, since the filament winding apparatus is structured such that a plurality of filaments is wound around the mandrel at one time, by considering simply, with only one rotation of the mandrel, a plurality of filaments can be wound around the mandrel at the same time.
For this reason, as compared to a case in which one filament is wound around the mandrel with one rotation of the mandrel, the number of rotations of the mandrel is determined by being divided by the number of filaments (wherein the number of filaments is n, 1/n times). Accordingly, time from the start of winding to the end thereof can be reduced thereby allowing production efficiency to be improved.
However, in such a structure as described above, a plurality of sets of filament feeding arrangements is required. Therefore, various problems are caused in a layout of such filament feeding arrangements.
In other words, an aspect of a layout of the filament feeding arrangements can be considered first in which the filament feeding arrangements are respectively disposed around the mandrel. However, if the filament feeding arrangements are structured as described above, when the mandrel is attached/detached with respect to supporting portions for supporting the mandrel, the supporting portions are interfered with the filament feeding arrangements thus making is extremely difficult to attach/detach the mandrel with respect to the supporting portions.
Further, another aspect of a layout of the filament feeding arrangements can also be considered first in which the filament feeding arrangements are arranged along a rotation radius direction or an axial direction of a rotation of the mandrel. However, in a case of such a structure, the apparatus as a whole becomes larger. Moreover, in the structure in which the filament feeding arrangements are arranged along a axial direction of a rotation of the mandrel, lengths of the filaments from the creel to the thread-feeding opening or those of the filaments from the thread-feeding opening to the take-up position at the mandrel are different from each other for each filament feeding arrangement thus causing possibility to vary tensional force or the like for each filament.
As yet another means for improving production efficiency, a structure can be considered in which a plurality of sets of supporting portions for supporting the mandrel is provided, and the filament feeding arrangements corresponding to the respective supporting portions can be provided.
In the case of this structure, during a winding of filament from the start to the end, filament can be wound around a plurality of sets of mandrels. Accordingly, a winding time which is determined by dividing the winding time of the filament around a plurality of sets of mandrels with the number of the mandrels can be reduced, whereby productivity can be improved.
Further, only one set of filament feeding arrangement is provided for one set of a mandrel. For this reason, deterioration of attachability/detachability of the mandrel by the mandrel being interfered with the filament feeding arrangement which is one of the problems when a plurality of sets of filament feeding arrangements is provided for one set of the mandrel, is difficult to occur.
Moreover, productivity can be improved without increasing the rotational speed of the mandrel. For this reason, a problem with an increase of the rotational speed of the mandrel is difficult to occur.
However, since a plurality of sets of supporting portions for supporting the mandrel or the plurality of sets of the filament feeding arrangements are provided and they are aligned each other, the apparatus becomes larger. Besides, since the supporting portions for supporting the mandrel or a plurality of sets of filament feeding arrangements are aligned each other, an apparatus which is able to use a large mandrel becomes much larger, which is not practical.